CVE-2025-66299

Security Sandbox Bypass with SSTI (Server Side Template Injection) in the Grav CMS

State: Published
Severity: 8.8 High
Published: Dec 1, 2025
Updated: Dec 2, 2025
Reserved: Nov 26, 2025

Description

Grav is a file-based Web platform. Prior to 1.8.0-beta.27, Grav CMS is vulnerable to a Server-Side Template Injection (SSTI) that allows any authenticated user with editor permissions to execute arbitrary code on the remote server, bypassing the existing security sandbox. Since the security sandbox does not fully protect the Twig object, it is possible to interact with it (e.g., call methods, read/write attributes) through maliciously crafted Twig template directives injected into a web page. This allows an authenticated editor to add arbitrary functions to the Twig attribute system.twig.safe_filters, effectively bypassing the Grav CMS sandbox. This vulnerability is fixed in 1.8.0-beta.27.

Scores

CVSS	Score	Vector	Source
3.1	8.8 High	CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H	GitHub_M

Weaknesses

CWE-94 Improper Control of Generation of Code ('Code Injection')
CWE-1336 Improper Neutralization of Special Elements Used in a Template Engine

Affected Products

Product	Versions
gravgetgrav	< 1.8.0-beta.27Affected

References

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